Arc-lamp.



J. T. H. DEMPSTER.

Y ARG LAMP.

APPLICATION FILED 1113.29, 1904. EENEWBD APR. v 1906.

905 ,800. v Patented Dec. 1, 1908.

2 SHEETS-SHEET 1.

lrwvertor: dohn'lLDempsteP,

www v J. T. H. DEMPSTER.

ARC LAMP.

APPLICATION FILED IBB. 29, 1904. BENEWIID APB. 7, 1906.

Patented Dec. 1,1908. 2 BKHBETS-SHBET 2.

Inventor V. +I. Dem pster, by TJGy.

' UNITED STATES PATENT oEEioE.

i AJOHN T. n. DEMPsTEn, OE soHENEoTADY, NEwlYoEx, ASSIGNOR To GENERAL ELECTRIC i COMPANY, A vCORPORATION or NEW YORK.

ARC-LAMP.

Patented Dec. 1, 1908.

Application flled February 29, 1904, Serial No. 195,781. Renewed April 7, 1906. Serial No. 310,473.

To all whom it may concern: v

Be it known that I, JOHN T. ITI. DEMPSTER, a citizen of the United States, residing at Schenectady, in the county of Schenectady, Stateof New York, have invented certain new and useful Improvements in Arc-Lamps,`

heated'the same electrodes may be good conductors throughout their length. This prop- `erty' may be characteristic of the material of which the electrode is originally made, or 1t `maybe a property possessed by the material formed by the action of the arc at the electrode tip. In Order to facilitate the starting of an arc from-[such an electrode, I have devised means. for heating the electrode at startingto increase its conductivity.

Where he material of which the negative electrode in direct-current lam s is made is suitably chosen, a flaming or luminous arc yieldingr an' intense light is obtained. In such cases the positive electrode may be so constructed that it is practically unconsu'med in the operation of the lamp.

The means for heatingthe electrode tip which I have devised is lshfowniin the drawings accom an 'n this s leciieation as embodied in-an are lamp in whichthe (positiyle by t e are. Some of the eatures of 'my invention y are peculiarly adapted for use in such an embodi'ment.

My invention in other' aspects however is not limitedto any particular form of embodiment.

The various features of novelty which characterize-any invention'are pointed out with particularity in the claims annexed to and forming a rt of l.this specification.

For a better understanding of my invention' however, reference may be had to the accomy anying drawings and -description in which I fiave illustrated,V and 'described somewhat in vdetailone embodiment of myinvention.

Of the drawings, Figure 1 is an elevation', partlyjingsection, of anarc lamp equip ed with,m-y`jinventiou; Fig. 2 is a sectional p an taken 'on' the line 2f-2. of Fig. 1; Fig. 3 is a dia ram illustrating the circu1t arrangements of t e lamp; and Fig. 4 is an elevation with parts in section, taken at right angles to the view shown in Fig. l. v

Referring to the drawings, a disk 1- is shown as representing the to member of the lamp mechanism proper. ber 2 screwed into a threaded aperture centrally located in the disk 1 is screw-connected at its upper end to the bracket 3 in which the lamp-supporting pulley insulator 4 is su orted. A hood 5 forming the top of t e amp casing is secured between the bracket 3 and the vtubular member 2.

tubular mem- Posts 6 extend downwardly from the under i side of the member 1 to which they are screw-connected. These posts have secured 'to them at their lower ends by means of screws 7 a pair of disk platforms 8 and 9 which are vparallel to eac other and to the disk 1. 'Spacing members 10 are employed to separate the platforms 8 and 9. Bolts 11 screwed into threaded apertures formed for ,Y the purpose in the. latforms Sand 9 carry at their lower end a t ird platform' 12 which is also parallel to the disk 1. A large aperture is centrally formed in the platform 12. A cylindrical member 1.3 is secured to the under side ofthe member 12 by lscrews 14 passing through extensions 15 from the member 13.

A disk-shaped member 16 formedof some material which is a good conductor both of heat and electricity, such as wrought copper, is held parallel to and about midway between the platforms 9 and l2 .by means of4 suitable space members or collars 17 and 18. The collars 18 at least are formed of insulating material and serve to insulate-the disk member 16 fromthe bolts 11.

A tubular member 1Q, preferably formed of wrought copper, is secured in a threaded aperture formedvcentrally in the member 16, the member 19 being formed with a collar or flange 20 which abuts against the under side ofthe member 16.` rIhe disk 16 and member 19 form the main positive electrode of the lamp. The disk 16 as formed and located has a large heat-dissipating capacity and carries heat away from the member 19 fast enough to prevent itsv destruction by the'arc" which extends from its lower end in the oper 13, the extreme lower end of the member 19 projecting somewhat s below the lower end of the cylindrical memtheljmember i115 The cores-31y of these coils' eoasoo ber 13. The upper end of the member 19 extends through an aperture formed for the purpose in the platform 9 terminating at about the level of the upper surface of that platform. A collar 21 formed of suitable ins ulating material such as porcelain or the like separates the tubular member 19 from the platform 9. The lower end of the member 19 is closed as shown in Fig. 1, the end wall of the member being considerably thicker than the side wall. A projection 22 extends axially a short distance upward from the end wall of the member.

-4 A pencil 23 of carbon or the like, somewhat smaller in diameter than the bore ofthe tubular member 19, extends into the tubular member 19. Normally its lower end rests on the u per end of they projection 22. As will be hereinafter explained, under some circumstances an arc is drawn between the projection 22 and the pencil 23 which forms an auxiliary electrode. As shown in Fig. 1 a cylindrical jacket 24 of suitable fire-proof insulating material, such as mica, lines the upper portion of the tube 19 and insulates that portion of the member from the pencil 2-3. A washer 25 of insulating material is clamped against' the upper end of the pencil 23 by a bolt 26 which i's screwed axially into the end of the pencil. The washer 25, which has a tin the ltubular member 2, positions the upper end of the pencil 23 centrally with respect to the memberZ. L, v

.pair of 'tubularmagnet coils 30 have. their `upper ends secured to the underside of are connected at' vtheir lower end ,by a yoke .member"32. .A post yfw'hich is carried byl jand extends upwardly from the yoke 32 has pivotally secured -to its upper'end the pawl member 34ofa clutch, the yoke '35 of which vsurrounds 4a tubular@ member o 'r sleeve 136i which in turn surroundsv the carbon pencil4 v23, belngjseparated therefrom by an ,insulating layer or bushing 37. The upper end of 'the tubular member 36 is secured to a crosshead 38. '.'Bolts'or rods 39 secured at oppoe sitepen'ds of the cross-head pass downwardly through'apertures formed for the purpose in thedisks 8, 9, 16 and 12'andiare secured at their lower ends to the ends 'of a yoke member 40. -The yoke member 40 carries on its upper' side and midway between its ends a socket 41 in whichfthe lower electrode l42 of the la'mp is held-in alinement with and below the tubular member 19.

Sleeves 43, threaded into the lplatform 9,.

g extend .through the' disks',v 16 and 12to a "n point somewhat below the lower end of the eo 'cylindrical member13 vand ,serve as guiding members infwhich the rods 39 haveasliding movement. Asis clearly'shown-in-Fig. 1

the apertures in the di k A16 throuo'h whi h thsl'eeves'43 pass are 'so formed' that the .disk

16 does notengage' the sleeve 43l but vjig,

to the post 44 near its upper end forms a sto against the u per surface of which the un er surface of t e ring 35 rests when the coils 3() are denergized and .the cores 31 assume their lowest position. An adjustable nut 46 on the post 44 near its lower end forms a stop against which the under side of the cross-head 23 rests in that condition of the apparatus. The post 44 which passes through an a erture formed for the purpose in the crossead 32 forms a vguide for positioning the cross-head.

Theleft-hand rod 39 as viewedin Fig. 1 is surrounded near its upper end by the sleeve portion 47 of a member`48. The outer end of the member 48`embraces a bolt 49 which extends between and is pivotally mounted.

bolt is turned toward the pawl, as'shown in Fig. 2'. A helical spring 52v which surrounds the 'up er end of the ,bolt 49 normally holds thebo t-.Switlll its Hat sidejaway from4 the jpawl 50. A handle 53v extending from 'a .collar 54 secured. to the bolt 49 at its lower end forms a means by which the ila-t side of the bolt 49 caribe turned to thepawl, as 'shown in`FigL..;2,jin which case the pawl will not'fenga e'fthev bolt.v ,Suitable means for limiting rt epivtal movement of the bolt 49v may.' belemploed; these may comprise' -proje'ctionsstrom `t e collar 54 which engage t eupperfprojecting end of one of thel bolts-11.ml v

When,- in a manner hereinafter explalned,

upper end of'the electrode' 42 strikes the lower end of the vtubuls'zr member 19, the sleeve 47. which slides loosely on the member 39 will atjrst 'beunaii'ected bythe movement of the,l rods.' After `'a'certain movement of the rodshowever a collar 55 adjustably secured upon the left-hand rod 39, as seen in Fig. 1, will engage the lower end of the sleeve 47 and thereafter the sleeve 47 and the member .48 will movev upward with'the rods 39, the pawl'50 being constructed to automatically release its engagement .with the-rod` 49 under these circumstances. When therods.39 start to move @downward however the pawl 50 will at once engage-the rod 49,.-thus lockingthesleevel 47 Y' from movement.` Y The downwardmovement of the rods 39 will end,` thereforewhen the -9 through an ap length struck after each feeding operationA between the end of the vtubular .member 19 and the end of the electrode 42 is ,thus limited to the play of the sleeve 47 between the crossehead 38 and the collar 55.

A pair of tubular magnet coils`56 have their u per ends secured to the under side of the dis r or platform 1. The movable cores coperating with these coils are connected at their lower end by cross-head'57. A rod or bar 58 adjustably connected to the crosshead 57 extends downwardly to a point adjacent the platform 9. A bushing 59 of insulating material extends from thc platform erture formed for the purpose-in the plat orm 8, and the lower end, of rod 58 plays in the bore of this bushing. A pawl- 60 of a clutch is pivoted to the rod 58 at the point 61. The yoke member 62.which cooperates with the 'pawl 60 surrounds the pencil 23. When the coils 56 are deenergized, the cores, cross-head 57 and rod 58 will drop down to the position'shown in Fig. 1. In this position the pencil 23 .will be free to move between the yoke and the pawl. When however the coils 56 are energized in"\theA manner hereinafter described7 the rod 58 will be elevated. This will cause the pawl 60 to first tilt and thereby lock the encil 23 between it and the yoke and therea ter move the pencil upward. A layer ofmaterial 62 such as mica insulates the awl 60 and yoke 62 from the disk 8. Anot er tubular magnet coil 63 is secured to the underside of the platform 1 with its axis vertical. The core 64 of the magnet coil 63 carries at its lower end a disk 65 of carbon or other good cone' ducting material. A pair of contact devices 67 and 68 are carried by or insulated from one of the posts 6 in such manner that ortions 67 and '68', the upper surfaces of w ich are in the same horizontal plane, form stops against'which the under surface of the disk 6 5 rests. When the coil 63-is denergized, in this position, the contacts 67 and 68 are electricallylconnected by the disk 65. When however t e coil 63 is energized the core 64 is raised andthe disk moves away from the portions 67 and 68 thus breaking the cir cuit between them.

A tubular member 70 extends from the lower surface of the latform 9 to the upper surface of the platvorm or disk4 1 passing through apertures for-med for the purpose in' the platforms 1, 8 and 9. The tubular member, which may be formed of metal, is surrounded by a layer 71 of material which is an insulator both of heat and electricity, and resistance conductor 72 may be wound about the outer surface of the `layer 71. It will be observed that the tubular member 70 forms itl/chimney or Ventilating pipe which leads casing.

the upper end of the conical member 77 to from the space" below platform 9 and discharges into the space between the 'disk 1 and the hood 5. ing material 71 serves to prevent the passing through the member 70 from heating the lamp mechanism. The air space between the plates 8 and 9 serves to prevent an undue transfer of heat from the chamber below the platform 9 to the lamp mechanism. To still further reduce the passage of heat, a layer 73 `of suitable insulating material such as asbestos-'may be' placed adjacent to the under side Vof the platform 9.

A cylindrical casing 74 surrounds the lamp I mechanism. located between the platforms and 9. Apertures' 75 andi76 located adjacent the lower and upper ends respectively of the casing 74vallow the ingress and egress respectively of suitable air currents for ven- ,tilating the lamp mechanism. A -conical shell meniber 77, the lower end of which closely embraces the cylindrical casing 74 to which it is attached, extends upward and outward to engage the top member 50i the A horizontal screen 79 extends from the casing 74. The casing 7 4" and the conical member 77 are also connected by an -annular diaphragm 80 parallel. to and located somewhat below the screen 79. Apertures 81 are formed in the member 77 between the diaphragm 80 and the screen 7 9 Apertures 82 are formed in themember 77 below the diaphragm 80 through which the air currents passing out of the lamp casing through the apertures 76 may pass. The gases passing upward. through the member 7() discharge into the atmosphere through the apertures 81, the screen 7 9 serving to tra any bulky arc products or the like carried y the gases.

An annular member 485 closely embraces the edges of the disks 9 and 12. -An extension of the member 85 below the platform 12 carries a series of nuts 86 through which screws 87 pass. The inner ends of these screws serve to support a globe 88 which surrounds the lower mechanism of the 1am Openings 85 formed inthe member 85ndmit air in proper amounts to the interior of the globe 88.-

The layer of heat-insulat-A 'frases The circuit arrangements of the lamp may be understood by referring to the diagram shown in Fig. 3. Lines 89 and 90 connected to a suitable source,lsupply current to the lamp. A conductor 91 extends from the line 89 to one terminal of the'resistance 72. The

- jection 22, anv arc will ture to a point at which it becomes con uct- `ing. As soon as the tip of the electrode 42 -cores 31 and thereby, through the rod 33 and p pounds of titanium, which are but poor con- .the arc between it and the pencil or electrode the ma et coil 30 is connected to one terminal of t 'e coil 56. The other terminal of the coil 56 is connected to the pencil 2 3 through the cross-head 57, rod 58 and clutch carried at the lower end of the r'od. v

y Assuming the initial outof-service condition of the lamp to be that shown in the. drawings; when the lines 8 9 and 90 are con, nected to the source of current, current will begin to flow between them to the conductor 91, disk 16, tubular member `19, pencil 23, coils 56, coils 30, contact 68', disk 6 5, contact 67, conductor y94, conductor 92.y The passage of current through thecoils 5 6will cause the cross-head 57, and thereby tle pencil 23, to be raised. As'v the lower end of the pencil 23 leaves then per end of the proe drawn between them whichwill rapidly heat the lower end of the tubular member 19. The passage of' current through the coils 30 will attract the clutch carried by it, raise tne tubular member 36, .cross-head 38, rods 39 and electrode 42 until lthe up er end of the electrode impinges vagainst t e lower end of the member 19. If for any reason-the electrical conf ductivity ofthe Aupper end of the electrode 42 is sufficiently poor when the electrode is cold no current will pass between the electrodes 19 and 42 at the tinstant of contact. The poor conductivity of theelectrode 42 when cold may be a pro erty of the material from which it is origina y formed, or itmay be a property'of the material into which the electrode or a portion of it is converted during the operation of the lamp. For instance, when the electrode is made of titanium carbid, which is a goed conductor both cold and when heated, the action of the arc eX- tending from the end of the electrode is to convert a layer or film of the titanium carbid at the electrode tip into one or more comductors of electricity when cold though when heated the conductivity of these compounds is fairly good. In any event the heat generated in the lower end of the member 19 by 23 will be rapidly transferred to the upper end of electrode 42, soon raising its tem erabecomes conducting, current will begin to flow between the lines 89 and 90 through the conductor 91, resistance 72, disk 16, member 19, electrodes 42, conductor 93, coil 63, conductor 92. The passage oi current throughl the coil 63 will lcause it to be energized, whereupon the armature'64 will move the disk away from the contacts 67 land 68', .thus breaking t-he circuit between them.4 When this occurs the coils 56 and 30 will both be denergized. This will allow the cores of lthe two electrodes.

In order to prevent the formation of tooA long an,y arc between the electrodes 19 and- .42,

potential coil 95 maye be connected between. theline 93 and the disk 16 in-shunt to the' are, as shown in Fig. 3. The core 96 of the coil 95 carries at its upper end a cross-head 97 of suitableconducting material. A sprin 98 ordinarily holds the cross-head 97 an core 96 in the position shown in Fig. 3. fWhen the voltage between the electrodes 19 and 42 rises be ond a predetermined amount the core 96 will be pulled downby the coil against the action of the sprin 98 until the cross-head rests upon a pair o contact devices 99 and 100. The contact device 99 is connected to the line 93 by conductor 101 while the contact 100 is connected'to the,

conductor 94 by conductor 102.

When the cross-head 97 engalges the con` tacts 99 and 100, it electrica y connectsthese contacts, and a low-resistance shunt comprising the conductor 101, contact 99,1 cross-head 97, contact 100, conductor 102, and conductor 94 isthusclosed about the coil 63.. The coil 63 will then be denergized and the disk 65 'will connect the contacts 67 and 68, whereupon the coils 56 and .30 will be energized in the manner hereinbefore described andthe electrode 42 will be moved v into contact with electrode 19, after whichva' new arc of the length equalto the play of the sleeve 47 between the cross-head 38 and the' collar 55 will be struck. Under some 'cir--v cumstances `the coil may be dispensed with. For this' reason this coil has not been shown in Figs. 1 and 2-of the drawings.4

The air currents reduced by the heat of thearc'pass upwar through the cylindrical -member-13l intothe chamber'formed between the platforms 9 and' 12 from which they will pass through the tubular member' 70, screen 7 9, and apertures 81 into the at-,

mosphere. These alr currents will serve to away the productssteady the arc and carry of combustion formed by the arc.

While I have hereinbe-iore' described the" bestform of my invention now known to me, I do not intend the claims which I have hereinafter made to be limited to the particularj form described and illustrated further than made necessary'by. the state of the art.

arc, and means for heating the-secondeleceeesgsoo `What I claim as newf and desire to secure by Letters Patent of the United States:is,

1. In combination, van electrode whose arcing end becomes a poor conductoriwhen cold, a second electrode proximity thereto and coperating therewith to maintain-.an

trode to raise the temperature` ci the'firstmentioned electrode and thereby increase its conductivity.

2. In combination, an electrode whose arcing end becomes a poor conductor when co d, a second electrode coperating therewith to establish and maintainan arc, and means for bringing the arcing ends of said electrodes into contact with each other'and heating the second electrode to increase the temperature and thereby the conductivity of the first electrode.

3. In combination, an electrode Whose arcing end becomes a poor conductor .when

cold, a second electrode coperating therewith to establish and maintainan arc," means for bringing said electrodes into engagement with each other, and means for ap lying heat to the second electrode until t e current iiowing. between said electrodes reaches .a predetermined value.

4. In combination, a non-consuming electrode, a consuming electrode in proximity thereto and coperating vtherewith to maintain an arc, and ymeans for heating the nonconsuming electrode `to thereby heat the consuming electrode.

5. In combination, a consuming. electrode whose arcingend becomes a poor conductor.

when cold, a .non-consuming electrode lin proximity thereto: and coperatin therewith .to maintain an arc, and means orheating the non-consumin electrode to thereby heat the arcing end o the consuming electrode and increase its conductivity.

6. In an-arc lamp, an electrode whose arcing end becomes a poor conductor when cold, a second electrode coperating therewith to maintain an arc, means for producing va relative movement between said electrodes to bring their arcing ends into engagement with each other, and means for heating vlthe said second electrode to increase the temperature and thereby the conductivity-of -the first electrode.

7. In an arc lamp, a consuming electrodewhose arcing` end becomes poorly-conducting when cold a non-consuming electrode co erating therewith to establish and'maintam an are, means for producing a relative movement between said electrodes to bring their arcing ends together, and means for heating the non-consuming electrode.

- 8. In an arc lamp, an electrode whose arcing end is of lower electrical conductivity at low temperatures than at high temperatures, a secon electrode coperating therewith to maintain an arc, meansffor producing a relative movement between said electrodes to cause their arcing ends to engage,A and means for applying heat tol said #second electrodeA until the current fioWing-between-the:-eiee trodes coperatingwith-Ieach other to maintain an arc, rfanauxiliary electnode, and means for simultaneously moving the fmain electrodes into engagement :with `eaclilotlrier and for drawingmn xarc fbetween-on'e-of the main electrodes and .the=.au;riliaryelectrode.

1 1. -In Acombination, :an electrode Whose' arcing end becomesba oor conductorwhen cold, .a second electro e co eratin there- Withto form anarc, rmeansiidr rouci'n a relative '-movementbetween sai 'electro es to brin their arcin endstofgetherfzansauxiliaryre ectrode, an means or maintainin an arcbetween said-auxiliary elect;rode.-anl said Isecond electrode until the current iiowing between themain electrodes reachesra predetermined value.

12. .Incombinatiom .a main electrode in the form-cfa tube closed at one end, asecond electrode cooperating with the main electrode to maintain anvarc, an auxiliary ele-ctrodeprojectinginto the bore of the tubular electrode, and means for drawing an arc between the closed end of the tubular electrode and the vauxiliary electrode.

13. In combination, a pair of main electrodes, Van auxiliary electrode, means for causing said :main electrodes -to be moved into engagement with each other and to separate so as to draw an arc, and independent means for starting an arc between one of said main electrodes and the auxiliary electrode.

14. In combination, a pair of electrodes coperating with each other to maintain an arc, and means for directly heating one of said electrodes to indirectly heat the other.

15. In combination, la pair of electrodes coperating with each other to start and maintain an arc between them, one of said electrodes requiring to be heated in order to make it operative for arcingpurposes, and

.means forheating the other of said electrodes directly to indirectly heatl the coperating electrode.

16. An electrode for arc lamps 'consistin of a tubular shell of metal having one en closed and provided with an inwardlyextending projection at the closed end. l

17. In an arc lam a threaded rod, an arc len th limiting sto aving a pawl carried byk an moving with t e support for the feeding f projection and the end of said auxiliary 55 -electrode,.

toothed Aside and one flat side, an arc englth `liniiting stop, having a 'pawl which norma yengages said toothed side, and means for 10 tur said flat side vtowards said pawl.

shell closed at one end, an electrode, one end of which pro'ects into said tubular member or shellfa t 'rd electrode, and meansforl 1 5 drawing an arc between one side ofthe endl l offsaid shell'and one of said electrodes, and

means for'thereafter drawing an arc between the other side of the end of said shell and the .othergof said electrodes. 20. Inv combination, a non-consuming'. electrode in the form of a shell o r tubular member closed at one end, a consuming elec- `trode, the arcing end of which may become non-conducting .when cold, means for moving `the consuming electrode into contact with the closed end of the tubular member or shell, means-for heating the interior of said tubular member orshell to thereby .heat the end of the consuming electrode and increase its conductivity, and means for "thereafter drawing an arc between the tubular'member or shell andthe consuming electrode. 21, In combination, a pair ofy mainl electrodes, an auxiliary electrode, means for moving said main electrodes into engagement with each other, and separate means for starting an arc between one of said main electrodes andthe auxiliary electrode.

'22. In combination, a main electrode, 'an

said main electrode, a second main electrode normally out of contact with thel first main electrode, and means for simultaneously moving the main electrodes together and separating the first-mentioned main e1ec' trode and the auxiliary electrode.

23. In combination, an electrodein the form of a tubular member or shell having one end closed andA formed with a projection extending centrally and interiorly from said closed end, an auxiliar electrode extending into said tubular or sheIl member, and means for drawing an arc between the `end .ofsaid 19. n combination, a tubular member'or state, an. auxiliary cathodeil Kauxiliary electrode normally in contact with 24. vIn'combination, a metal electrode, a

cooperating non-metal electrode, means for maintaining-jan larc .between the electrodes. .60

:25.1Inan arclamp, the combination of a,

mam cathode and an yauxiliary cathode, an

anode-fof; good heat :conductivity in arcing r:relation to bothcathodes, and shieldingv the .niaiiircathode from the 'auxiliary arc.

.6- In an arc lam a cathode that is a.4

onductor'of e ectricity in the cold and an anode f that is' a good conductor-of eat in the cold state in arcing relation to both cathodesand 27. In an arc lamp, the combination of an anode of a material that'i's av good conductor of heat, a cathode that is a poor conductor of electricit in the cold state,' and means for 75 heating -t e cathode tol conductivity by convduction of heat through vthe anode.

28. In an arc lamp, .the combinationf an anode that is a'good conductor of heat interposed between a cathode which is a conductor'of the'seco'nd class and an auxiliary cathode, means for starting an auxiliary arc and thereby yheatin the main cathode by conduction throug the anode, and means for starting an arc betweenI the anode and the main cathode and breaking the auxiliary arc. A

29. In an arc lamp, the combination of an anode of a material that is a good conductor 'of heat, a cathode-which is a poor conductor Vof-electricity in the cold state, an auxiliary cathode in arcing relationvto the anode remote from the main cathode, and means for starting an auxiliary arc and thereby heating -the main cathode to conductivity by heatconduction from the anode'. 95l .30.- In an arc lamp, the combination of a cathode that is a conductor of theseco'nd class, an auxiliary cathode, yan anode that is a "good conductor' of heat'- interposed between them, means for starting an-aum'liary 100 arc whereby the main cathode is heated t0 conductivity by conduction through the anode, and means for starting the main arc 'when theV main cathode has become sufficiently conducting'.v 105 Inwitness whereof'I have hereunto se't my handthis 26thv day ,of February 1904.

` JOHN Tg 'DEMrsTERf Witnesses: I

BENJAMIN IB. HULL, -HEENf-Onroan 

